Formed article from hydraulic composition

ABSTRACT

It is an object of the present invention to provide moldings of hydraulic composition derived from hydraulic composition, to which both mechanical workability and wear resistance are simultaneously imparted, thereby achieving the applicability to a portion or part for which wear resistance is required, and ease of molding and shaping. According to the present invention, the molding of hydraulic composition prepared by press-molding a hydraulic composition, which comprises a hydraulic powder, a non-hydraulic powder having an average particle diameter of {fraction (1/10)} or less of that of the hydraulic powder and a workability improver, to form a molded product, then curing the molded product to form a cured product, and then providing one of a metallic coating and a metallic compound coating on the cured product.

FIELD OF THE INVENTION

This invention relates to moldings of hydraulic composition.

BACKGROUND OF THE INVENTION

Hitherto, metallic materials are broadly used as materials formechanical parts due to their various excellent materialcharacteristics. In these years, needs for mechanical parts areincreasing as a result of advances in technologies. Specifically,mechanical parts using sintered ceramics, plastics or any other nonmetalmaterials are frequently used to cover shortcomings of metallicmaterials.

However, it is a current circumstance that conventional materials hardlycope with all of various needs in the progress of the technicalinnovation. Accordingly, there exists a demand for materials applicableto mechanical parts having novel characteristics.

In order to satisfy those demands, new materials are continuouslydeveloped. Under this trend, various techniques for forming ahigh-strength cured product by a hydraulic composition for theapplication to mechanical parts are proposed. For example, JapanesePatent Application Laid-open No. Sho-61-215239 disclosesultrahigh-strength mortar and concrete formed by a compositioncontaining as main constituents a cementitious substance and ultrafinepowder, high-range water reducing agent, water and aggregate. JapanesePatent Application Laid-open No. Sho-62-52157 discloses a high-strengthcured product derived from the introduction of metallic particles into acementitious admixture. Japanese Patent Application Laid-open No.Hei-03-137047 discloses a combined material of a cementitious substanceand polymer. However, these cementitious cured products have yet putinto practical use due to their poor strength and workability.

In order to address those problems, the present inventors made variousstudies and found that a molding produced by using a hydrauliccomposition resulted from the combination of a hydraulic powder,non-hydraulic powders having an average particle diameter of {fraction(1/10)} or less of that of the hydraulic powder, workability improver,moldability improver and the like possess exhibits an excellent propertyachieving the applicability to sheet-feeding rollers or any othermechanical parts. Consequently, they filed a patent application(Japanese Patent Application Nos. Hei-11-28137, and Hei-11-59310).

However, cured products of those hydraulic compositions must furtherimprove the surface hardness for the application to mechanical partsrequiring a higher wear resistance. Needs to mechanical parts are notonly for wear resistance, but also for improved electric conductivity,magnetic property, electromagnetic wave shielding property, heatshielding property, and other various properties. Consequently,conventional moldings of hydraulic composition hardly satisfy theseneeds.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a molding ofhydraulic composition that is capable of being applied to a portion orpart requiring wear resistance and easily be molded and machined byimparting both mechanical workability and wear resistance to a curedproduct derived from a hydraulic composition.

It is another object of the present invention to impart electricconductivity, electromagnetic wave shielding property, optical property,heat shielding property, decorability or the like to the molding derivedfrom the hydraulic composition.

The present inventors made intensive studies to achieve the aboveobjects and found that a molding produced by press-molding a hydrauliccomposition (A) derived from a mixture of mixed powders comprised of ahydraulic powder and a non-hydraulic powder having an average particlediameter of {fraction (1/10)} or less of that of the hydraulic powderand a workability improver and then curing the resultant possesses anexcellent workability, dimensional resistance and other properties; themolding can be imparted with both excellent mechanical workability andwear resistance by forming a plated layer on a surface of the molding;and the molding can also be imparted with electric conductivity,magnetic property, electromagnetic wave shielding property, heatshielding property, or other various properties by properly selectingthe type of plated coating to be formed on the molding. Consequently,the present invention has been achieved.

Specifically, according to the present invention, there is provided amolding of hydraulic composition prepared by press-molding a hydrauliccomposition, which comprises a hydraulic powder, a non-hydraulic powderhaving an average particle diameter of {fraction (1/10)} or less of thatof the hydraulic powder and a workability improver, to form a moldedproduct, then curing the molded product to form a cured product, andthen providing one of a metallic coating and a metallic compound coatingon the cured product.

The hydraulic composition of the molding preferably comprises 100 wt.part of a powdered mixture that contains 50-90 wt. % of the hydraulicpowder and 10-50 wt. % of the non-hydraulic powder having an averageparticle diameter of {fraction (1/10)} or less of that of the hydraulicpowder, and 2-18 wt. part of the workability improver.

The workability improver in the molding of hydraulic composition ispreferably at least one selected from the group consisting of vinylacetate resin, vinyl acetate acrylate copolymer resin, vinylacetate-Veova copolymer resin, vinyl acetate maleate copolymer resin,vinyl acetate ethylene copolymer resin, vinyl acetate-ethylene-vinylchloride copolymer resin, acrylic copolymer resin, acrylic-styrenecopolymer resin, acrylic-silicone copolymer resin, vinyl acetate-Veovaternary copolymer resin and epoxy resin.

The one of the metallic coating and the metallic compound coating ispreferably formed by wet plating, spray plating, vacuum deposition,sputtering, chemical vapor deposition, ion plating or activated reactiveevaporation process.

The molding used for the molding of hydraulic composition may be curedby natural curing, steam curing or autoclaving curing process.

The present inventors found that a hydraulic composition (B) containinga hydraulic powder, a non-hydraulic powder having an average particlediameter of {fraction (1/10)} or less of that of the hydraulic powder, amoldability improver, a workability improver and a viscosity improverpossesses an excellent extrusion molding property; a molding produced bysubjecting the hydraulic composition (B) to the extrusion-molding andsubsequently the curing process possesses an excellent workability,dimensional resistance and the like; the molding can be imparted with animproved wear resistance in addition to the excellent machinability byforming a metallic coating or metallic compound coating on a surface ofthe molding; and the molding can also be imparted with electricconductivity, magnetic property, electromagnetic wave shieldingproperty, heat shielding property, or other various properties byproperly selecting the type of metallic coating or the metallic compoundcoating to be formed on the molding. Consequently, the present inventionhas been achieved.

Specifically, according to the present invention, there is provided amolding of hydraulic composition prepared by extruding a hydrauliccomposition, which comprises a hydraulic powder, a non-hydraulic powderhaving an average particle diameter of {fraction (1/10)} or less of thatof the hydraulic powder, a moldability improver, a workability improverand a viscosity improver, to form an extruded product, then curing theextruded product to form a cured product, and then providing one of ametallic coating and a metallic compound coating on the cured product.

The hydraulic composition preferably comprises 100 wt. part of apowdered mixture that contains 40-80 wt. % of the hydraulic powder,10-50 wt. % of the non-hydraulic powder having an average particlediameter of {fraction (1/10)} or less of that of the hydraulic powderand 10-20 wt. % of the moldability improver, 2-9 wt. part of theworkability improver, and 0.5-5 wt. part of the viscosity improver.

The workability improver in the molding of the hydraulic composition maybe at least one selected from the group consisting of vinyl acetateresin, vinyl acetate acrylate copolymer resin, vinyl acetate-Veovacopolymer resin, vinyl acetate maleate copolymer resin, vinyl acetateethylene copolymer resin, vinyl acetate-ethylene-vinyl chloridecopolymer resin, acrylic copolymer resin, acrylic-styrene copolymerresin, acrylic-silicone copolymer resin, vinyl acetate-Veova ternarycopolymer resin and epoxy resin.

The moldability improver in the molding of hydraulic composition may betalc.

One of the metallic coating and the metallic compound coating in themolding of hydraulic composition may be formed by wet plating, sprayplating, vacuum deposition, sputtering, chemical vapor deposition, ionplating or activated reactive evaporation process.

The molding used for the molding of hydraulic composition may be curedby natural curing, steam curing or autoclaving curing process.

As a hydraulic composition for manufacturing a molding, the composition(A) that contains the hydraulic powder, the non-hydraulic powder and theworkability improver, or the composition (B) that contains the hydraulicpowder, the non-hydraulic powder, the moldability improver, theworkability improver and the viscosity improver is used in the presentinvention.

The description will be hereinafter made for a method of manufacturingmoldings based upon various components used in each composition and therespective compositions.

Hydraulic Composition

(1) Hydraulic powder:

The hydraulic powder used in the present invention is meant to be apowder that is capable of curing by contact with water, illustrativeexamples of which include a powder of a member selected from calciumsilicate, calcium aluminate, calcium fluoroaluminate, calciumsulphoaluminate, calcium aluminoferrite, phosphate calcium, hemihydrategypsum or anhydride gypsum, or calcium oxide possessing a self-hardeningproperty, or a mixed powder of at least two members selected from them.As a representative example of it, it can be cited a powdered membersuch as Portland cement. It is possible to solely use one type of thehydraulic powder or use the admixture of two or more types of thehydraulic powders.

The hydraulic powder preferably has an average particle diameter ofabout 10-40 μm, and has a specific surface area by blaine of 2500 cm²/gor more to secure the hydration performance for the strength of themolding.

The content of the hydraulic powder in the case of (A) is preferably setin the range of about 50-90 wt. % and more preferably about 65-75 wt. %with the total content of the hydraulic powder and the non-hydraulicpowder as being 100 wt. %. The content of the hydraulic powder in thecase of (B) is preferably set in the range of about 40-80 wt. % and morepreferably about 45-55 wt. % with the total content of the hydraulicpowder, the non-hydraulic powder and the moldability improver as being100 wt. %. Where the content of the hydraulic powder is excessivelysmall, the strength, filling ratio or the like of the resultant moldingwill be degraded. On the other hand, where the content of the hydraulicpowder is excessively large, the filling ratio required for producingthe molding will be degraded. Moldings produced from the compositions inboth cases are not suitable since they are unlikely to be tolerableagainst machining stress and may pose any other problems.

(2) Non-hydraulic powder:

The non-hydraulic powder used in the present invention is meant to be apowder that is incapable of curing by itself even by contact with waterand include a powder that has components eluted therefrom in alkaline oracid state, or under high-pressure steam atmosphere and then reactedwith other eluted components, thereby generating a matter. Illustrativeexamples of the non-hydraulic powder include powdered potassiumhydroxide, dihydrate gypsum, calcium carbonate, slag, flyash, silica,clay and silica fume. It is possible to solely use one type of thenon-hydraulic powder or use the admixture of two or more types of thenon-hydraulic powders.

The non-hydraulic powder must have an average particle diameter of{fraction (1/10)} or less and preferably of {fraction (1/100)} or lessof that of the hydraulic powder. The lower limit of the particlediameter is not necessarily set, but may be varied in such a range asnot to ruin the effects of the present invention. In usual application,it is preferable to employ an average particle diameter of about{fraction (1/500)} or more of the hydraulic powder, since the averageparticle diameter of less than this value lowers the flowability, andhence deteriorate the moldability. The use of the non-hydraulic powderhaving such a particle diameter can enhance the filling ratio forforming the molding, reduce the void ratio of the resultant molding andhence improve the dimensional resistance of the same.

The content of the non-hydraulic powder in the case of (A) is preferablyset in the range of about 10-50 wt. % and more preferably about 25-35wt. % with the total content of the hydraulic powder and thenon-hydraulic powder as being 100 wt. %. The content of thenon-hydraulic powder in the case of (B) is preferably set in the rangeof about 10-50 wt. % and more preferably about 20-30 wt. % with thetotal content of the hydraulic powder, the non-hydraulic powder and themoldability improver as being 100 wt. %. Where the content of thenon-hydraulic powder is excessively small, the filling ratio will bedegraded. On the other hand, where the content of the non-hydraulicpowder is excessively large, the strength and the filling ratio will bedegraded, and the molding's solid state properties after molding andsubsequent curing processes in both cases will be undesirably affected.That is, the molding may be chipped off or the dimensional resistancemay be undesirably affected. Considering the mechanical strength, it ispreferable to adjust the content of the non-hydraulic powder so as notto excessively lower the filling ratio.

(3) Moldability improver:

The moldability improver used in the present invention is meant to be amaterial that is capable of improving the slippability between a moldingdie and a molding during forming the molding from the hydrauliccomposition by extrusion-molding, reducing the anisotropy of themolding, stabilizing the quality of the same, illustrative examples ofwhich include talc (hydrated magnesium silicate), mica and otherplate-like substances. These plate-like substances possess an excellentorientation property, so that they impart slippability on the surface ofthe molding, reduce the resistance with respect to a molding die, andhence achieve easy operation of the extrusion molding. They can alsoreduce the anisotropy on the quality of the molding, and stabilize thequality of the molding.

The content of the moldability improver is preferably set in the rangeof about 10-30 wt. % and more preferably about 15-25 wt. % with thetotal content of the hydraulic powder, the non-hydraulic powder and themoldability improver as being 100 wt. %. Where the content of themoldability improver is excessively small, the slippability of themolding will be lowered, causing increase in resistance to the moldingdie. Hence, the molding accuracy will be degraded. Additionally, theanisotropy of the molding will undesirably become great, which resultsin undesirable effects over the mechanical strength, dimensionalresistance or other properties.

(4) Workability improver:

The workability improver is meant to be a material that possesses aproperty contributing to improvements in moldability, unmoldability,cutting/grinding property, grinding accuracy, or other properties, andmore particularly a material effectively contributing to improvements incutting/grinding property and grinding accuracy of the molding formedfrom the hydraulic composition.

According to the hydraulic composition containing such workabilityimprover, the workability improver fulfills the function as a moldingauxiliary agent during the press-molding operation, so that themoldability is improved. Also, the workability improver improves thefragile of a cement-type cured product, so that the resultant molding isunlikely to be damaged when removed from the die. Hence, the workingefficiency is improved. The molding produced from the hydrauliccomposition which is a fragile material is easy to crack during thecutting operation, thereby posing problems of material cracking orchipping. Accordingly, the workability improver is mixed into thehydraulic composition, thereby imparting the resultant molding withtoughness, which stimulates the machinability of the molding as a solidmaterial, and hence successfully preventing the molding from cracking orchipping. Therefore, it is possible to improve the machinability of theresultant molding derived from the hydraulic composition, which isconventionally hard to be machined such as cut or ground, to the samelevel as a metallic material. As a result, the cutting by a latheturning machine and grinding by a cylindrical grinding machine can beperformed in nearly the same manner as a metallic material, allowing forprecise machining of the molding required for having a predeterminedsize in μm order.

Illustrative examples of the workability improver applicable to thepresent invention include vinyl acetate resin, copolymer resincontaining vinyl acetate, acrylate resin, copolymer resin containingacrylic monomer, styrene resin, copolymer resin containing styrene, andepoxy resin. As the copolymer resin containing vinyl acetate in thesemembers, it can be cited vinyl acetate acrylate copolymer resin, vinylacetate-Veova copolymer resin, vinyl acetate maleate copolymer resin,vinyl acetate ethylene copolymer resin, vinyl acetate-ethylene-vinylchloride copolymer resin, and vinyl acetate-Veova ternary copolymerresin can be cited. As the copolymer resin containing acrylic monomer inthose members, acrylic, vinyl chloride and vinyl acetate copolymerresin, acrylic-styrene copolymer resin, and acrylic-silicone copolymerresin can be cited. As the copolymer resin containing styrene, it can becited styrene butadiene copolymer resin and the like. It is possible tosolely use one type of the workability improver or use the admixture oftwo or more types of the workability improvers. The workability improvermay be used in powder, emulsion or other form, and preferably has asingle particle diameter of about 1 μm or less in usual application.

The content of the workability improver in the case (A) is preferablyset as a solid content of the workability improver in the range of about2-18 wt. part and more preferably about 5-15 wt. part with the totalcontent of the hydraulic powder and the non-hydraulic powder as being100 wt. part. Also, the content of the workability improver in the case(B) is preferably set as a solid content of the workability improver inthe range of about 2-9 wt. part and more preferably about 6-8 wt. partwith the total content of the hydraulic powder, the non-hydraulic powderand the moldability improver as being 100 wt. part. Where the content ofthe workability improver is excessively small, the cuttability will bedegraded. On the other hand, where the content of the workabilityimprover is excessively large, the grinding accuracy and dimensionalresistance after the grinding will be undesirably lowered, although themoldability is improved.

(5) Viscosity improver:

The viscosity improver is meant to be a material that is capable ofdissolving in water and hence develop the viscosity, and a componentthat is effective such as for enhancing particle-to-particle bondingbetween the hydraulic powder and the non-hydraulic powder, therebypreserving the shape of the resultant molding, retaining thewater-holding capacity and producing a solid molding.

Illustrative examples of the viscosity improver usable in the presentinvention include methylcellulose, hydroxyethyl cellulose, andcarboxymethyl cellulose. The quantity of the viscosity improver consumedis preferably about 0.5-5 wt. part and more preferably 3-4 wt. part withthe total content of the hydraulic powder, the non-hydraulic powder andthe moldability improver as being 100 wt. part. Where the content of theviscosity improver is excessively small, it is likely to cause cracks inan edge part of the excluded product, or rough surface or any otherundesirable effects on the molding quality. On the other hand, where thecontent of the viscosity improver is excessively large, it is likely toincrease shrinkage ratio, and degrade dimensional resistance of aproduct.

Method of Manufacturing a Molding

(1) Molding Process

With respect to (A)

For manufacturing a molding by using the hydraulic composition (A), theaforesaid respective components are mixed with added water according toneeds, and then the resultant is press-molded.

The content of water is preferably about 30 wt. part or less and morepreferably 25 wt. part or less with the total content of the hydraulicpowder and the non-hydraulic powder as being 100 wt. part. The contentof water is preferably set as small as possible for decreasing dryingshrinkage. Polymer emulsion usually exists a water dispersion having aconcentration of about 40-50%. Accordingly, where the polymer emulsionis used as the workability improver, the content of water separatelyadded is preferably set as small as possible since water present in theemulsion is mixed into each component. For example, where 18 wt. part ofthe polymer emulsion is added with the total content of the hydraulicpowder and the non-hydraulic powder as being 100 wt. part, a sufficientamount of water to be added is about 10 wt. part. Where water issupplied from the outside of the molding during the curing process, amuch smaller amount of water is sufficient.

The mixing process is not necessarily limited to a specific one,provided that the respective components of the hydraulic composition canbe uniformly mixed together. Particularly, for uniformly mixing acomposition containing the hydraulic powder and the non-hydraulic powderhaving an average particle diameter of {fraction (1/10)} or less of thehydraulic powder, it is preferable to employ a mixing process enablingapplication of high shearing force. For example, it is possible toemploy a ribbon mixer, Henschel mixer, Eirich mixer and the like. Aperiod of time required for the mixing can be shortened by using mixersof these types that can exert a high shearing force.

For imparting an excellent handling property to a mixture for themolding operation, the admixture may be granulated to a size suitablefor a shape to be molded after the mixing. A conventional process suchas a rolling granulating process, compression granulating process andstirring granulating process can be employed.

The hydraulic composition thus mixed is then filled into a molding dieand press-molded into a predetermined shape. A molding process is notnecessarily limited to a specific one. For example, isostatic pressing,multi-axial pressing, single-axial pressing and the like may beemployed. As a pressing condition, a pressing force is preferably highenough to approximate as close to a calculated theoretical concentrationas possible. Since the lower limit of the pressing force is variedaccording to a moldability of the mixture, water content ratio, requireddimensional accuracy or the like, it may be properly determined basedupon these conditions. The pressing force required for molding isusually in the range of about 0.5-1.5 ton/cm², and preferably about0.8-1.2 ton/cm². Where the pressing force for molding is excessivelylow, the cured product is unlikely to be solidified, and therefore has alowered mechanical strength. On the other hand, where the pressing forcefor molding is excessively high, the polymer emulsion is likely to flowfrom the inside of the molding, and therefore causes deteriorated solidstate properties of a cured product. The excessively low and highpressing forces are therefore undesirable.

With respect to (B)

For manufacturing a molding by using the hydraulic composition (B), theaforesaid respective components are mixed with added water according toneeds, and then the admixture is subjected to extrusion molding.

The content of water is preferably in the range of about 10-30 wt. partand more preferably about 20-25 wt. part with the total content of thehydraulic powder, the non-hydraulic powder and the moldability improveras being 100 wt. part. Where the content of water is excessively low,molding is hardly made, and it is likely to cause cracks or the like onthe molding and deteriorate the mechanical properties of the molded andcured product. On the other hand, where the content of water isexcessively large, retaining the shape of the molded product is hardlymade, and it is likely to cause shrinkage of the molded cured productand deteriorate the dimensional resistance. Thus, excessively low andhigh water contents are undesirable.

The mixing process is not necessarily limited to a specific one,provided that the respective components of the hydraulic composition canbe uniformly mixed together. Particularly, for uniformly mixing acomposition containing the hydraulic powder and the non-hydraulic powderhaving an average particle diameter of {fraction (1/10)} or less of thehydraulic powder, it is preferable to employ a mixing process providingfor high shearing force such as by kneading the composition with akneader or the like. A period of time required for the mixing can beshortened by using a mixer of the type exerting a high shearing force.

For imparting an excellent handling property to an admixture for moldingoperation, the admixture may be granulated to a size suitable for ashape to be molded after the mixing. As a granulating process, aconventional process such as the rolling granulating process,compression granulating process and stirring granulating process can beemployed.

The hydraulic composition having the aforementioned specific contentratio of each component possesses an excellent extrusion moldingproperty, allowing itself to be easily extruded into a molding having apredetermined shape by following a conventional process.

As an example of the extrusion molding process, it may employ a processincluding throwing the mixed and kneaded material by a kneader in anextruder, and extruding the material under an extrusion pressure of 30kg/cm² -100 kg/cm² while deaerating it by a vacuum pump.

(2) Curing Process

The molding formed in the above manner is then removed from the moldingdie and then cured for such a period of time as to allow the molding tohave a sufficient strength. The curing may be made by leaving themolding at a room temperature. Alternatively, it is possible to employsteam-curing or other process. Among various processes, the molding ispreferably cured in an autoclave. Where the content of water for formingthe cured product is lacking or insufficient, the steam curing processis preferably carried out.

The autoclaving curing is preferably carried out under a saturated vaporpressure of 7.15 kg/cm² or higher and at a temperature of 165° C. orhigher, and more preferably under a saturated vapor pressure of 9.10kg/cm² or higher. The curing time depends on a curing temperature. Forexample, where the curing is conducted at 175° C., the curing maycontinue for about 5-15 hours. It is preferable that the compressionstrength is raised to about 5N/mm² or more, after finishing the moldingand before starting the autoclaving curing. The case where a sufficientstrength has not yet been developed until the start of the autoclavingcuring is not preferable since there may cause explosion of the moldingduring the autoclaving.

The steam curing may be conducted for 10-24 hours at a temperature ofabout 60° C.

The molding produced in the above manner possesses an excellentmoldability, unmoldability, cutting property, grinding property,grinding accuracy or other properties, allowing the molding itself to beeasily molded and formed into various shapes by machining. According tothe present invention, a metallic coating or metallic compound coatingis formed on a surface of the thus formed molding, thereby improving thesurface hardness of the molding, and hence imparting the wear resistanceto the molding. Also, it is possible to impart electromagnetic waveshielding property, optical property, heat shielding property,decorability or the like to the molding according to the type of acoating to be formed.

The forming process of the metallic coating or the metallic compoundcoating is not necessarily limited to a specific one, and therefore aconventional forming process can be applied. As an example of suchforming processes, it can be cited wet plating, spray plating, vacuumdeposition, sputtering, chemical vapor deposition, ion plating,activated reactive evaporation process (ARE process) or the like.

The metallic coating or metallic compound coating may be formed in theusual manner according to a process employed. The type of a coating alsois not necessarily limited to a specific one, and therefore may beproperly selected from metallic coatings or metallic compound coatingsformable by conventional processes according to an intended purpose. Asan example of the metallic compound coating, it can be cited a metaloxide, metal nitride, metal carbide or metal boride coating. Thethickness of a coating is also not limited to a specific one, andtherefore may be properly varied according to an intended purpose.

Where a plated coating is made by the wet plating process, the processis such that the electroless plating is conducted to impart electricconductivity to the surface of the molding of hydraulic composition, andthen electroplating is conducted.

The electroless plating may be conducted as following the usual manner.For example, a sensitizer-activator process, catalyst process or anyother conventional process may be conducted to apply catalyst forelectroless plating to the surface of the molding and form anelectroless-plated coating by using a conventional electroless platingsolution such as an electroless copper plating solution and electrolessnickel plating solution. The thickness of an electroless plated coatingis not necessarily limited to a specific one. For example, in order toimpart a proper electric conductivity, the thickness may be in the rangeof about 0.2-0.5 μm.

Then, a plated coating is formed by the electroplating process. The typeof an electroplating solution is not necessarily limited to a specificone, and therefore may be properly selected from conventionalelectroplating solutions according to an intended purpose. For example,it is possible to use a nickel plating solution, copper platingsolution.

Since the electroless plated coating is usually thinner, it ispreferable to avoid the electroplating conducted at a blast and a highcurrent density. According to a preferable example, a copper platedcoating or nickel plated coating having a thickness of 1-3 μm is formedas a primer plating at a relatively low current density such as that ofabout 0.5 A/dm², and a nickel plated coating or the like having athickness of about 5-20 μm is preferably formed on the primer plating.According to needs, a chrome plated coating having a thickness of about5-20 μm may be formed as an outermost layer.

The metallic composition coating such as metal oxide, metal nitride,metal carbide, metal boride coating may be formed by spraying processsuch as flame spray, plasma spray, explosion spray coating process,following conventional conditions.

The molding of hydraulic composition of the present invention having themetallic coating or metallic composition coating has a relatively highsurface hardness with respect to a conventional hydraulic composition,so that it possesses an excellent wear resistance. Also, the moldingpossesses an excellent moldability, unmoldability, cutting property,grinding property, grinding accuracy or other properties, allowing themolding itself to be easily molded and formed into various shapes bymachining. Also, it is possible to impart electric conductivity,electromagnetic wave shielding property, optical property, heatshielding property, decorability or the like to the molding by properlyselecting the type of a coating. The molding is also applicable to partsof electronic devices.

Thus, according to the present invention, it is possible to manufacturea molding of hydraulic composition that is applicable to a partrequiring the wear resistance, and possesses various properties such aselectric conductivity, electromagnetic wave shielding property, opticalproperty, heat shielding property and decorability in a cheap manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a molding with a nickel plated coatingformed thereon according to a first embodiment.

FIG. 2 is a cross section of a molding with a nickel plated coating anda chrome plated coating formed thereon according to a second embodiment.

FIG. 3 is a cross section of a molding with a coating layer made of anadmixture of Al₂O₃ and TiO₂ according to a third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the description will be made for the present invention based uponthe respective embodiments.

(First Embodiment)

FIG. 1 is a cross section of a molding of hydraulic composition with aplated coating formed thereon according to the present invention, inwhich reference numerals 1, 2, 3, 4 and 5 respectively represent amolding of hydraulic composition, a catalyst layer (palladium), a nickellayer formed by the electroless plating process, a primer nickel platedlayer formed by the electroplating process, and a nickel plated layerformed by the electroplating process. The method of manufacturing thecured product will be hereinafter described.

With respect to (A)

20-30 wt. part of water was added to the hydraulic composition (A)containing 70 wt. part of Portland cement as the hydraulic powder(average particle diameter of about 15 μm), 30 wt. part of silica fumeas the non-hydraulic powder (average particle diameter of about 0.2 μm)and 10 wt. part of acrylate resin as the workability improver, and mixedtherewith by using a Henschel mixer.

The admixture was then filled in a molding die and press-molded by usinga press molding machine under a molding pressure of 500 kg/cm², so thata molding having a size of 30×50×500 mm was produced. This molding wasthen unmolded and heated to 175° C. and 9.1 atmospheric pressure at aprogramming rate of 50° C./hour, then held for 7 hours at 175° C. and9.1 atmospheric pressure, and returned to atmospheric pressure in 3hours by the autoclaving curing process. After the curing, the resultantwas cut into a piece having a width of 10 mm. Thus, a molding 1A havinga size of 30×30×10 mm was produced.

With respect to (B)

20-30 wt. part of water was added to the hydraulic composition (B)containing 80 wt. part of Portland cement as the hydraulic powder(average particle diameter of about 15 μm), 10 wt. part of silica fumeas the non-hydraulic powder (average particle diameter of about 0.2 μm),10 wt. part of talc as the moldability improver, 10 wt. part of acrylateresin as the workability improver and 2 wt. part of carboxymethylcellulose as the viscosity improver, and mixed therewith by using akneader.

The admixture was then molded into a piece having a size of 30×30×500 mmby an extrusion molding machine at a pressure of 10 kg/cm² whiledeaerating the admixture by a vacuum pump, then heated to 175° C. and9.1 atmospheric pressure at a programming rate of 50° C./hour, then heldfor 7 hours at 175° C. and 9.1 atmospheric pressure, and returned toatmospheric pressure in 3 hours by the autoclaving curing process. Theresultant was cut into a piece having a width of 10 mm. Thus, a molding1B having a size of 30×30×10 mm was produced.

The moldings 1A and 1B were immersed in a catalyzer solution as asolution for the electroless plating for 5 minutes at a room temperatureby using a catalyzer (a solution of the admixture of tin ions andpalladium ions), then rinsed, and then immersed in a sulphuric acidsolution, so that palladium 2 as a catalytic substance for theelectroless nickel plating was applied on a surface portion (30×30 mm)of each of the moldings 1A and 1B.

Then, the moldings 1A and 1B were immersed in a electroless nickelplating bath (a solution containing nickel sulphate, sodium citrate,sodium hypophosphite and ammonia) at 30° C. for 5 minutes. Thus, anelectroless nickel layer 3 having a thickness of 0.5 μm was formed on asurface of each of the moldings 1A and 1B.

Subsequently, a primer nickel plated layer 4 having a thickness of 2 μmwas formed on a surface of each of the moldings 1A and 1B by conductingthe electro-nickel plating process at a cathode current density of 0.5A/dm² by using an electro-nickel plating solution (a solution containingnickel sulphate, nickel chloride and boric acid), and a nickel platedlayer 5 having a thickness of 15 μm was formed thereon by conducting theelectro-nickel plating process at a cathode current density of 1 A/dm²by using the same electro-nickel plating solution.

(Second Embodiment)

In the same manner as the first embodiment, the moldings of hydrauliccomposition 1A and 1B each were provided thereon with the palladiumcatalyst layer 2, the electroless nickel layer 3, the primer nickelplated layer 4 by the electroplating process, and the nickel platedlayer 5 by the electroplating process.

Then, a hard chrome layer 6 having a thickness of 20 μm was formed onthe nickel plated surface of each of the moldings by conducting theplating at a solution temperature of 60° C. and a cathode currentdensity of 50 A/dm² for 10 minutes by using a chrome plating solution(175 g/l of chromic acid and 0.7 g/l of sulphuric acid).

FIG. 2 illustrates a cross section of the thus produced molding.

(Third Embodiment)

The moldings of hydraulic composition 1A and 1B were produced in thesame manner as the first embodiment. Then, a coating layer 7 made of amixture of Al₂O₃ and TiO₂ was formed on each of the moldings by theexplosion spray coating process.

The thus formed coating layer was an oxide coating having a thickness of200 μm, a melting point of 1700° C. or higher and the weight % ratio ofAl₂O₃ to TiO₂ of 4 to 1.

FIG. 3 is a cross section of the thus produced molding.

Surface hardness test:

The surface hardness for each of the moldings produced in the first tothird embodiments was measured by the Vickers hardness test, and themeasured results are shown in Table 1. As a comparative example, thesurface hardness for a molding with no plated coating formed thereon isalso shown in Table 1.

TABLE 1 SURFACE HARDNESS (HV) SURFACE [MOLDING [MOLDING TREATING PROCESS1A] 1B] EMBODIMENT NICKEL PLATING 525 520 1 EMBODIMENT NICKEL PLATINGplus 900 940 2 CHROME PLATING EMBODIMENT Al₂O₃ plus TiO₂ 1250 1150 3COMPARATIVE NO TREATMENT 50 40 EXAMPLE

1. A molding of hydraulic composition prepared by press-molding ahydraulic composition, which comprises a hydraulic powder, anon-hydraulic powder having an average particle diameter of {fraction(1/10)} or less of that of the hydraulic powder and a workabilityimprover, to form a molded product while having a compression strengthset at 5 N/mm² or more, then curing the molded product by an autoclavingcuring process under a saturated vapor pressure of 7.15 kg/cm² or higherand at a temperature of 165° C. or higher to form a cured product, thenapplying catalyst for electroless plating to the surface of the curedproduct, then forming an electroless-plated coating thereon, and thenproviding a metallic coating on the cured product by an electroplatingprocess.
 2. The molding of hydraulic composition according to claim 1,wherein said hydraulic composition comprises 100 wt. part of a powderedmixture and 2-18 wt. part of the workability improver, said powderedmixture containing 50-90 wt. % of the hydraulic powder and 10-50 wt. %of the non-hydraulic powder having an average particle diameter of{fraction (1/10)} or less of that of the hydraulic powder.
 3. Themolding of hydraulic composition according to claim 1, wherein saidworkability improver is at least one selected from the group consistingof vinyl acetate resin, vinyl acetate acrylate copolymer resin, vinylacetate-Veova copolymer resin, vinyl acetate maleate copolymer resin,vinyl acetate ethylene copolymer resin, vinyl acetate-ethylene-vinylchloride copolymer resin, acrylic copolymer resin, acrylic-styrenecopolymer resin, acrylic-silicone copolymer resin, vinyl acetate-Veovaternary copolymer resin and epoxy resin.
 4. A molding of hydrauliccomposition prepared by extruding a hydraulic composition, whichcomprises a hydraulic powder, a non-hydraulic powder having an averageparticle diameter of {fraction (1/10)} or less of that of the hydraulicpowder, a moldability improver, a workability improver and a viscosityimprover, to form an extruded product while having a compressionstrength set at 5 N/mm² or more, then curing the extruded product by anautoclaving curing process under a saturated vapor pressure of 7.15kg/cm² or higher and at a temperature of 165° C. or higher to form acured product, then applying catalyst for electroless plating to thesurface of the cured product, then forming an electroless-plated coatingthereon, and then providing a metalliccoating on the cured product by anelectroplating process.
 5. The molding of hydraulic compositionaccording to claim 4, wherein the hydraulic composition comprises 100wt. part of a powdered mixture, 2-9 wt. part of the workabilityimprover, and 0.5-5 wt. part of the viscosity improver, the powderedmixture containing 40-80 wt. % of the hydraulic powder, 10-50 wt. % ofthe non-hydraulic powder having an average particle diameter of{fraction (1/10)} or less of that of the hydraulic powder and 10-20 wt.% of the moldability improver, 2-9 wt. part of the workability improver.6. The molding of hydraulic composition according to claim 4, whereinthe workability improver is at least one selected from the groupconsisting of vinyl acetate resin, vinyl acetate acrylate copolymerresin, vinyl acetate-Veova copolymer resin, vinyl acetate maleatecopolymer resin, vinyl acetate ethylene copolymer resin, vinylacetate-ethylene-vinyl chloride copolymer resin, acrylic copolymerresin, acrylic-styrene copolymer resin, acrylic-silicone copolymerresin, vinyl acetate-Veova ternary copolymer resin and epoxy resin. 7.The molding of hydraulic composition according to claim 4, wherein themoldability improver is talc.
 8. A molding of hydraulic compositionprepared by press-molding a hydraulic composition, which comprises ahydraulic powder, a non-hydraulic powder having an average particlediameter of {fraction (1/10)} or less of that of the hydraulic powderand a workability improver, to form an extruded product while having acompression strength set at 5 N/mm² or more, then curing the moldedproduct by an autoclaving curing process under a saturated vaporpressure of 7.15 kg/cm² or higher and at a temperature of 165° C. orhigher to form a cured product, and then providing a metallic compoundcoating on the cured product by a spraying process.
 9. A molding ofhydraulic composition prepared by extruding a hydraulic composition,which comprises a hydraulic powder, a non-hydraulic powder having anaverage particle diameter of {fraction (1/10)} or less of that of thehydraulic powder, a moldability improver, a workability improver and aviscosity improver to form an extruded product while having acompression strength set at 5 N/mm² or more, then curing the excludedproduct by an autoclaving curing process under a saturated vaporpressure of 7.15 kg/cm² or higher and at a temperature of 165° C. orhigher to form a cured product, and then providing a metallic compoundcoating on the cured product by a spraying process.